Cost guide
Second Story Addition Cost in 2026
Building up avoids a new foundation and keeps your yard, but it means structural work and living through construction. Price your addition below.
Step 1 of 4
Your addition
Size and type.
Labor costs differ a lot by state. This adjusts every line.
New finished floor area, not counting the existing house.
Type of addition
Foundation
Estimated addition cost
$113,900
$73,000 – $154,800
The calculator above starts as a ground-floor room. Open it set to a second story to price a bedroom-and-bath suite.
Second-story cost by size
| Scenario | Estimated range | Per sq ft |
|---|---|---|
| Small second-story room (300 sq ft) | $83,600 – $171,000 | $279–$570 |
| Bedroom and bath suite (500 sq ft) | $147,400 – $303,000 | $295–$606 |
| Large two-bedroom addition (700 sq ft) with bath | $198,000 – $399,000 | $283–$570 |
Estimates at national-average pricing, calculated with our own pricing engine and reviewed September 2026. Change the inputs in the calculator to price your exact project.
Second-story cost per square foot
All-in, a second-story addition costs about $270–$550 per square foot, against $235–$485 for a ground-floor room. You skip the foundation, but structural reinforcement and rebuilding the roof make every square foot cost more. Larger second stories cost less per square foot than small ones.
Second-story cost by size (no bathroom)
| Scenario | Estimated range | Per sq ft |
|---|---|---|
| 400 sq ft second storyAbout 20 × 20 ft, a bedroom and a hall | $108,900 – $219,000 | $272–$548 |
| 800 sq ft second storyA full floor over a small ranch house | $210,100 – $411,000 | $263–$514 |
| 1,000 sq ft second storyA full floor over an average single-story home | $260,700 – $507,000 | $261–$507 |
Estimates at national-average pricing, calculated with our own pricing engine and reviewed September 2026. Change the inputs in the calculator to price your exact project.
Adding a bathroom to any of these adds about $12,000–$30,000 before contingency.
What drives second-story cost
- Type matters most: a second story costs more per sq ft than a ground-floor room, but needs no new foundation.
- Bathrooms and kitchens are plumbing-heavy and can add $30k–$70k.
- Architect fees, permits and utility tie-ins are often missing from rough quotes.
- Additions carry more unknowns, so this estimate includes a larger contingency.
Frequently asked questions
How much does a second story addition cost?
It depends on size, scope and finish level. A second story needs no new foundation but does need structural reinforcement and a new roof, so it usually costs more per square foot than a ground-floor room. See the table above for current ranges.
How much does a second story addition cost per square foot?
About $270–$550 per square foot, all-in, as a national average for a 400 sq ft addition. That compares with $235–$485 for a ground-floor room. Your state, finish level and any bathroom or kitchen change the number, so use the calculator above for a local estimate.
How much does an 800 or 1,000 sq ft second story cost?
About $210,000–$411,000 for 800 square feet and $261,000–$507,000 for 1,000 square feet, without a bathroom. A 400 sq ft second story costs about $109,000–$219,000.
How much does a second story over a garage cost?
A two-car garage is typically 400 to 600 square feet, so price it like the 400 and 500 sq ft rows above. Garage walls and slabs are often not built to carry a second floor, so expect an engineer to specify reinforcement. Get the structure checked before you plan the layout.
Can I add a second story to any house?
Most single-story homes can support a second story, but your foundation, load-bearing walls and roof structure must be evaluated by a structural engineer.
Do I need to move out during construction?
For most second story additions you can remain in the home. Expect noise, dust and limited access to the work area for 3–6 months.
Related guides
- Bedroom Addition Cost in 2026A bedroom addition is priced like any room addition: size, foundation and finish level matter most.
- Bathroom Addition Cost in 2026A new bathroom needs plumbing, a vent, a waterproof finish and its own share of the addition fixed costs.
- Mudroom Addition Cost in 2026A mudroom is a small bump-out at an entry, so the fixed costs of an addition (design, permits, roof tie-in) make up much of the price.
- Roof Replacement Cost in 2026Material is the biggest lever, but pitch, height and the condition of the decking underneath decide how far the number moves.
- HVAC Installation Cost in 2026System type, home size and efficiency set the base price.